Semiconductor device and manufacturing method thereof

ABSTRACT

As a result of miniaturization of a pixel region associated with an improvement in definition and an increase in a substrate size associated with an increase in area, defects due to precision, bending, and the like of a mask used at the time of evaporation have become issues. A partition including portions with different thicknesses over a pixel electrode (also referred to as a first electrode) in a display region and in the vicinity of a pixel electrode layer is formed, without increasing the number of steps, by using a photomask or a reticle provided with an auxiliary pattern having a light intensity reduction function made of a diffraction grating pattern or a semi-transmissive film.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a light emitting device using a lightemitting element which generates fluorescence or phosphorescence byapplying an electric field to the element provided with a layercontaining an organic compound (hereinafter referred to as an “organiccompound layer”) between a pair of electrodes, and a manufacturingmethod of the light emitting device. Note that the light emitting devicerefers to an image display device, a light emitting device, and a lightsource (including a lighting system).

2. Description of the Related Art

A light emitting element using an organic compound as a luminous body,which has features such as thinness, lightness, high-speed response, andDC drive at low voltage, is expected to be applied to a next-generationflat panel display. In particular, a display device in which lightemitting elements are arranged in matrix is considered to have anadvantage in a wide viewing angle and excellent visibility over aconventional liquid crystal display device.

It is said that as for a light emitting mechanism of the light emittingelement, light is emitted by applying a voltage between a pair ofelectrodes where an organic compound layer is interposed, so thatelectrons injected from a cathode and holes injected from an anode arerecombined with each other at a light emitting center of the organiccompound layer to form molecular excitons and the molecular excitonsrelease energy when returning to a ground state. Singlet excitation andtriplet excitation are known as excited states, and it is thought thatlight emission can be achieved through either of the excited states.

For the light emitting device in which light emitting elements arearranged in matrix, a driving method such as passive matrix driving(simple matrix type) or active matrix driving (active matrix type) canbe used. However, when the pixel density is increased, the active matrixtype where each pixel (or each dot) is provided with a switch is thoughtto be advantageous because it can be driven at lower voltage.

In the case of manufacturing an active matrix light emitting device, aTFT is formed over a substrate having an insulating surface as aswitching element, and EL elements each of which uses a pixel electrodeelectrically connected to the TFT as an anode or a cathode are arrangedin matrix.

In the case of manufacturing an active matrix light emitting device or apassive matrix light emitting device, a partition for insulatingadjacent pixels from each other is formed at an end portion of the pixelelectrode.

The applicant of the present invention has proposed partitions disclosedin References 1 and 2 (Reference 1: Japanese Patent Laid-Open No.2002-164181, and Reference 2: Japanese Patent Laid-Open No.2004-127933).

In a display device provided with an electroluminescent (hereinafteralso referred to as EL) element, a color light emitting element whichemits color light is used in order to perform full-color display. It isone of important factors to form a light emitting material of each colorover an electrode in a minute pattern in order to form a color lightemitting element.

For the above purpose, a method for forming into a minute pattern usinga mask is generally used when forming a material using an evaporationmethod or the like.

However, as a result of miniaturization of a pixel region associatedwith an improvement in definition and an increase in a substrate sizeassociated with an increase in area, defects due to precision, bending,and the like of a mask used at the time of evaporation have becomeissues.

SUMMARY OF THE INVENTION

The present invention provides a structure which prevents a defect dueto precision, bending, and the like of a mask used at the time ofevaporation without increasing the number of steps.

Demands for higher definition, higher aperture ratio, and higherreliability on a full-color flat panel display using emission colors ofred, green, and blue has been increased. Such demands are major issuesin advancing miniaturization of each display pixel pitch associated withan improvement in definition (increase in the number of pixels) and areduction in size of a light emitting device. It is necessary to reducealso the upper surface shape of a partition in order to improvedefinition of an active matrix light emitting device or a passive matrixlight emitting device. The present invention provides a partition whichrealizes display with higher definition by reducing the upper surfaceshape and a light emitting device including that partition.

According to the present invention, a partition including portions withdifferent thicknesses over a pixel electrode (also referred to as afirst electrode) in a display region and in the vicinity of a pixelelectrode layer is formed, without increasing the number of steps, byusing a photomask or a reticle provided with an auxiliary pattern havinga light intensity reduction function made of a diffraction gratingpattern or a semi-transmissive film.

The partition of the present invention supports an evaporation mask withits thick portion, and prevents the evaporation mask from being incontact with the surface of a pixel electrode due to kinking, bending,or the like of the evaporation mask. Accordingly, the surface of thepixel electrode is not damaged by the mask and the pixel electrode doesnot have a defective shape. Therefore, a display device which canperform high-definition display and has high reliability can bemanufactured. The thick portion may be formed selectively as long as itcan prevent the evaporation mask from being in contact with the surfaceof the pixel electrode. In other words, one thick portion may be formedin a region where a plurality of pixels is arranged.

In addition, a thin portion of the partition of the present inventioncan suppress the generation of covering failure at the boundary of thepixel electrode and the partition in forming a layer containing anorganic compound over the pixel electrode. Therefore, the partition ofthe present invention is particularly effective when forming anextremely thin layer containing an organic compound. The thickness ofthe thin portion of the partition is at least half or less that of thethick portion.

By adjusting the photomask or reticle provided with an auxiliary patternhaving a light intensity reduction function made of a diffractiongrating pattern or a semi-transmissive film, the width of the thickportion can be reduced, and the total width of the partition includingthe width of the thin portion can be less than 20 μm. In addition, evenif pressure is applied from the evaporation mask at the time ofevaporation when the width of the thick portion of the partition is setto approximately 5 μm, the strength is secured because the thin portionssupport the thick portion from both sides.

One configuration of the invention disclosed in this specification is alight emitting device having a plurality of light emitting elements overa substrate having an insulating surface, where the light emittingelement includes a first electrode, a partition covering an end portionof the first electrode, a layer containing an organic compound over thefirst electrode, and a second electrode over the layer containing anorganic compound, and the partition has a cross-sectional shape whichspreads from an upper surface of the light emitting element toward thesubstrate, and has a step on a side of the partition.

In the above configuration, one feature is that an upper end portion ofthe partition is rounded. Being rounded at the upper end portion of thepartition means that the partition has a curved surface determineddepending on the center of curvature located inside the partition whencut along a plane perpendicular to the substrate plane and the curvatureradius is 0.2 μm to 3 μm. In order to form the upper end portion of thepartition to be rounded, a photosensitive resin is preferably used as amaterial of the partition and selectively exposed to light when formingthe partition. Alternatively, the upper end portion of the partition maybe rounded by wet etching. Further, in the cross-section of thepartition, the partition has two curved surfaces determined depending onthe centers of curvature located inside the partition at two portions,the upper end portion and the lower end portion, and also one curvedsurface determined depending on the center of curvature located outsidethe partition between the two portions.

In the above configuration, another feature is that the partition havinga cross-sectional shape which spreads toward the bottom is a singlelayer. Since it does not have a stacked structure, a manufacturingprocess for the partition is simple.

In addition, as a means of solving the problem different from theabove-described means, a structure which supports an evaporation maskmay be formed around a pixel portion where a light emitting element isarranged, that is, a display region. In this specification, a protectivelayer formed between a certain light emitting element and another lightemitting element is referred to as a partition. In addition, in thisspecification, an insulator which is located outside a light emittingelement positioned apart from the center of a pixel portion and outsidewhich the light emitting element is not positioned is referred to as astructure. When the area of a display region is small, an evaporationmask can be prevented from being in contact with the pixel electrodesurface due to kinking, bending, and the like by forming a structurewhich supports the evaporation mask around the display region.

Another configuration of the present invention is a light emittingdevice including a pixel portion having a plurality of light emittingelements over a substrate having an insulating surface, where the lightemitting element includes a first electrode, a partition covering an endportion of the first electrode, a layer containing an organic compoundover the first electrode, and a second electrode over the layercontaining an organic compound, where a structure made of the samematerial as the partition is arranged to surround the pixel portion, anda thickness of the structure and that of the partition are differentfrom each other.

The structure can also be formed in the same step using the samematerial as the partition having a cross-sectional shape which spreadstoward the bottom. In the above configuration, one feature is that thepartition comprises a protruding portion. The partition has across-sectional shape which spreads from the upper surface of the lightemitting element toward the substrate and has a step on a side of thepartition.

In the case of sealing the light emitting element using an opposingsubstrate, the structure may serve to maintain a distance between a pairof substrates. In the above configuration, one feature is that the lightemitting device includes a substrate opposed to the substrate having aninsulating surface and the structure maintains a distance between thepair of substrates. This configuration is particularly effective whenusing a light transmitting substrate as the opposing substrate andperforming display by passing light emitted from the light emittingelement through the light transmitting substrate. Since the structurecan maintain a uniform distance between the pair of substrates,high-definition display can be achieved.

In the above configuration, another feature is that a region surroundedby the structure and the pair of substrates is filled with a resin. Thisconfiguration is particularly effective when using a light transmittingsubstrate as the opposing substrate and performing display by passinglight emitted from the light emitting element through the lighttransmitting substrate. In addition, by filling a space between the pairof substrates with a transparent resin, overall transmittance can beincreased as compared to that of a space between the pair of substrateswithout being filled with anything (inert gas).

In addition to the above-described structure and the above-describedpartition, various structures such as a projection for improvingadhesiveness when attaching to the sealing substrate can be formed inthe same step using the same material.

A configuration of the invention for realizing the above-describedconfiguration is a method for manufacturing a light emitting device,including the steps of forming a first electrode over a substrate havingan insulating surface, forming a partition having a thick region and athinner region using a photomask or a reticle having a diffractiongrating pattern or a semi-transmissive portion over an end portion ofthe first electrode, forming a layer containing an organic compound overthe first electrode, and forming a second electrode over the layercontaining an organic compound.

In the above manufacturing steps, one feature is that the partition is aresin formed by selective light exposure and development using aphotomask or a reticle having a diffraction grating pattern or asemi-transmissive portion.

In the above manufacturing steps, the step of forming the layercontaining an organic compound over the first electrode is effectivebecause a thick region of the partition can prevent bending or the likeof the evaporation mask in the case of using an evaporation method,specifically, a resistance heating method using an evaporation mask. Inaddition, the layer containing an organic compound can be formed by aspin coating method, an ink-jet method, a dipping method, anelectrolytic polymerization method, or the like without limitation to anevaporation method.

Another configuration of the invention related to a manufacturing methodis a method for manufacturing a light emitting device having a pluralityof thin film transistors and a plurality of light emitting elements overa substrate having an insulating surface, which includes the steps offorming a thin film transistor including a semiconductor layer having asource region, a drain region, and a channel formation regiontherebetween, a gate insulating film, and a gate electrode over a firstsubstrate having an insulating substrate, forming a first electrodewhich is electrically connected to the source region or the drain regionover the gate insulating film, forming a partition which covers an endportion of the first electrode, and a structure in a positionsurrounding the plurality of light emitting elements, forming a layercontaining an organic compound over the first electrode, forming asecond electrode over the layer containing an organic compound, andsealing the light emitting element by attaching a second substrate tothe first substrate with a resin material so that the structuremaintains a distance between the substrates.

In the manufacturing steps, one feature is that the partition and thestructure are made of the same material and are resins formed byselective light exposure and development using a photomask or a reticlehaving a diffraction grating pattern or a semi-transmissive portion.Since the structure can be formed in the same step as the partition, itcan be formed without increasing the number of steps.

The present invention can be applied to not only an active matrix lightemitting device having a switching element but also a passive lightemitting device.

Note that the light emitting device in this specification refers to animage display device, a light emitting device, or a light source(including a lighting system). Further, the light emitting deviceincludes all of the following modules: a module having a light emittingdevice provided with a connector such as an FPC (Flexible PrintedCircuit), a TAB (Tape Automated Bonding) tape, or a TCP (Tape CarrierPackage); a module having a TAB tape or a TCP provided with a printedwiring board at the end thereof; and a module having an IC (IntegratedCircuit) directly mounted on a light emitting element by a COG (Chip OnGlass) method.

The present invention can prevent defects due to precision, bending, orthe like of a mask used at the time of evaporation, without increasingthe number of steps, by providing a partition which covers an endportion of the first electrode and a structure which surrounds a pixelportion.

In addition, the present invention can reduce the size of the partition,particularly, the plane area the partition occupies and can realize asmall-sized partition and a light emitting device including thepartition. In particular, as a distance between the evaporation mask andthe first electrode is reduced using the partition, wraparound of anevaporated film can be suppressed and coloring accuracy of theevaporated film can be improved. Note that the wraparound of theevaporated film means the act of forming an evaporated film in a largerregion than the area of an opening of an evaporation mask at the time ofevaporation using the evaporation mask. The present invention canadvance miniaturization of each display pixel pitch associated with animprovement in definition (increase in the number of pixels) and areduction in size of a light emitting device. The partition of thepresent invention can reduce a distance between an evaporation mask anda first electrode and surely prevent contact between the first electrodeand the evaporation mask. Therefore, an evaporation mask designed to bethinner can also be used.

BRIEF DESCRIPTION OF DRAWINGS

FIGS. 1A to 1C are cross-sectional views showing a process of thepresent invention.

FIGS. 2A and 2B are diagrams showing an example of an evaporationapparatus.

FIG. 3 is a diagram showing an example of a cross-sectional structure ofthe present invention.

FIGS. 4A and 4B are diagrams showing an example of a cross-sectionalstructure of the present invention.

FIGS. 5A to 5C are diagrams showing a manufacturing process for a lightemitting device.

FIGS. 6A to 6C are diagrams showing a manufacturing process for a lightemitting device.

FIGS. 7A and 7B are diagrams showing a manufacturing process for a lightemitting device.

FIGS. 8A to 8C are diagrams showing a manufacturing process for a lightemitting device.

FIGS. 9A and 9B are diagrams showing a manufacturing process for a lightemitting device.

FIG. 10 is a diagram showing a structure of an active matrix lightemitting device.

FIG. 11 is an example of a top view of a pixel region.

FIGS. 12A and 12B are diagrams showing electronic devices to which thepresent invention is applied.

FIGS. 13A and 13B are diagrams showing an electronic device to which thepresent invention is applied.

FIG. 14 is a diagram showing an electronic device to which the presentinvention is applied.

FIGS. 15A to 15D are diagrams showing electronic devices to which thepresent invention is applied.

FIG. 16 is a diagram showing an example of a cross-sectional structureof the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Embodiment modes of the present invention are hereinafter explained indetail with reference to the accompanying drawings. However, the presentinvention is not limited to the following explanation. As is easilyknown to a person skilled in the art, the mode and the detail of thepresent invention can be variously changed without departing from thespirit and the scope of the present invention. Therefore, the presentinvention is not interpreted as being limited to the followingdescription of the embodiment modes. Note that the same referencenumeral is used to denote the same portion or a portion having a similarfunction among different diagrams in a structure of the presentinvention to be explained below, and repetitive explanation is omitted.

Embodiment Mode 1

Here, the present invention is explained using an example of an activematrix light emitting device.

In addition, an example of a manufacturing process for obtaining astructure of FIG. 1C is hereinafter described.

First, a TFT 16 is manufactured over a substrate 10 having an insulatingsurface. As for a base insulating film 12 of the TFT 16 and a stackedlayer 17 of insulating films including a gate insulating film, aninorganic material (such as silicon oxide, silicon nitride, siliconoxynitride, a SiOF film, or a SiONF film) obtained by a sputteringmethod or a PCVD method is used. As for an insulating film 18functioning as an interlayer insulating film, an inorganic material(such as silicon oxide, silicon nitride, silicon oxynitride, a SiOFfilm, or a SiONF film) obtained by a sputtering method, a PCVD method,or a coating method; a photosensitive or non-photosensitive organicmaterial (such as polyimide, acrylic, polyamide, polyimide amide, aresist, or benzocyclobutene) obtained by a coating method; an SOG film(an insulating film having a siloxane structure) obtained by a coatingmethod; a stacked layer thereof; or the like can be appropriately used.As for the TFT 16, an n-channel TFT or a p-channel TFT may bemanufactured by a known method.

Next, an opening is formed to reach an electrode of the TFT by etchingthe insulating film 18, and then a first electrode 13 serving as ananode is formed so as to overlap with the electrode of the TFT. Here,the first electrode 13 is formed using a conductive film having a highwork function (such as an indium tin oxide (ITO) film, an alloy film ofindium oxide and zinc oxide (In₂O₃—ZnO), or a zinc oxide (ZnO) film) bywet etching. In selectively etching the first electrode 13, etchingconditions or materials are appropriately set so as to be able to have aselection ratio with the insulating film 18.

Subsequently, an insulating film is entirely formed by a coating method,and then a partition 11 is formed using a photomask or a reticleprovided with an auxiliary pattern having a light intensity reductionfunction made of a diffraction grating pattern or a semi-transmissivefilm. The partition 11 is formed in a position which overlaps with theopening reaching the electrode of the TFT. It is preferable to form thepartition 11 in a position which overlaps with the opening reaching theelectrode of the TFT because adhesiveness between the partition and thefirst electrode is improved. Here, an example of entirely forming aphotosensitive resin film 20 and then exposing it to light by using aphotomask provided with an auxiliary pattern having a light intensityreduction function made of a semi-transmissive film is described withreference to FIG. 1A.

In FIG. 1A, a light exposure mask 400 is provided with a light blockingportion 401 made of a metal film such as Cr, and a portion provided witha semi-transmissive film (also referred to as a semi-transmissiveportion) 402 as an auxiliary pattern having a light intensity reductionfunction. In the cross-sectional view of the light exposure mask, thewidth of the light blocking portion 401 is denoted by t2 and the widthof the portion 402 provided with a semi-transmissive film is denoted byt1. A portion of the portion 402 provided with a semi-transmissive filmoverlapped with the light blocking portion 401 does not transmit light.Here, the example of using a semi-transmissive film as a part of thelight exposure mask is described; however, a diffraction grating patternmay be used.

When the photosensitive resin film 20 is exposed to light using thelight exposure mask shown in FIG. 1A, a light-unexposed region and alight-exposed region are formed. At the time of light exposure, lightpasses around the light blocking portion 401 and passes through theportion 402 provided with a semi-transmissive film, so that alight-exposed region indicated by dotted lines in FIG. 1A is formed.Then, the partition 11 having a cross-sectional shape which spreadstoward the bottom is formed by removing the light-exposed region. Inother words, the partition 11 includes a thick portion and a thinportion as shown in FIG. 1A. The thin portion of the partition is formedto have a thickness at least half or less that of the thick portion.Note that the thick portion refers to a portion where a thicknessmeasured from a flat surface of the insulating film 18 is large. Whenthe height of the partition 11 (that is, the height of the thickportion) is 2 μm or more, defective coverage tends to be generated.Therefore, the height of the partition 11 is preferably small (less than2 μm). As shown in FIG. 1A, a partition having a different width fromthe partition 11 overlapping with the opening reaching the electrode ofthe TFT is formed above a wire 19.

Hereinabove, the example of forming the partition using thephotosensitive resin film 20 is described; however, the partition 11having a cross-sectional shape which spreads toward the bottom may beformed by entirely forming an insulating film, forming a resist maskusing a photomask or a reticle provided with an auxiliary pattern havinga light intensity reduction function made of a diffraction gratingpattern or a semi-transmissive film, and performing etching using theresist mask as a mask.

Next, a layer 14 containing an organic compound is formed by anevaporation method. In the case of forming by an evaporation method, thelayer 14 containing an organic compound is selectively formed using anevaporation mask 21 as shown in FIG. 1B. Note that FIG. 1B shows upsidedown with respect to the actual evaporation direction. In the case ofperforming evaporation, a substrate is sandwiched between a substrateholder and an evaporation mask; a permanent magnet provided in thesubstrate holder attracts the evaporation mask made of metal and fixesthe substrate; and evaporation is performed with an evaporation sourcelocated below an exposed surface of the first electrode.

Although FIG. 1B shows the layer 14 containing an organic compound as asingle layer, the layer 14 containing an organic compound has a stackedstructure of a hole injection layer (or a hole transport layer), a lightemitting layer, an electron injection layer (or an electron transportlayer), and the like. Note that in order to improve reliability,deaeration is preferably performed by performing vacuum heating (100° C.to 250° C.) shortly before forming the layer 14 containing an organiccompound. For example, in the case of using an evaporation method,evaporation is performed in a film formation chamber which is evacuatedto a vacuum of 5×10⁻³ Torr (0.665 Pa) or less, preferably, 10⁻⁴ Pa to10⁻⁶ Pa. In evaporation, an organic compound is vaporized in advance byresistance heating and scattered toward the substrate when a shutter isopened at the time of evaporation. The vaporized organic compound isscattered upwards and evaporated over the substrate through an openingprovided in an evaporation mask.

FIGS. 2A and 2B show an example of an evaporation apparatus.

The evaporation apparatus shown in FIG. 2A includes a film formationchamber provided with an evaporation shield for maintaining asublimation direction of an evaporation material, and the evaporationshield is provided with a plurality of openings. The evaporationmaterial is sublimated through the plurality of openings. An evaporationsource which is movable in a direction perpendicular to the movingdirection (also referred to as a transfer direction) of a substrate isprovided under the evaporation shield. Further, the width Wb of theevaporation shield is broader than the width Wa of the substrate, sothat uniformity of the thickness of an evaporated film is improved. Themechanism of the evaporation apparatus is briefly described below.

A substrate 701 is aligned with an evaporation mask 702 in advance. Thesubstrate is transferred to the direction indicated by an arrow(sublimation direction 706 of an evaporation material) in the alignedstate. The substrate is transferred so as to pass over an evaporationshield 703 a. The evaporation shield 703 a has an opening 703 b, and anevaporation material from an evaporation source 704 is sublimatedthrough the opening 703 b. The evaporation shield 703 a is heated sothat the evaporation material does not attach to the evaporation shielditself, in order to maintain the sublimation direction 706 of theevaporation material from the opening 703 b.

The evaporation source 704 can be provided with a plurality ofcrucibles, and can be moved in the direction indicated by an arrow (amoving direction 705 of the evaporation source). A resistance-heatingmethod is used as an evaporation method. Further, the range of movementof the evaporation source is desirably broader than the width Wa of thesubstrate. Further, the width Wb of the evaporation shield is alsopreferably broader than the width Wa of the substrate, so thatuniformity of the thickness of an evaporated film is improved.

Note that, in the evaporation apparatus of FIG. 2A, the shape and thenumber of the openings 703 b are not limited in particular.

In order to supply an evaporation material to the crucible in theevaporation source, a setting chamber may be provided which connects tothe film formation chamber through a gate. Further, a plurality ofevaporation sources and evaporation shields may be provided in one filmformation chamber. A top view of an evaporation apparatus in which oneevaporation source provided with a plurality of crucibles and a settingchamber are provided, is shown in FIG. 2B. A setting chamber 707 isprovided in the moving direction 705 of the evaporation source. Theevaporation material may be supplied by moving the evaporation source tothe setting chamber. In the case where the evaporation source is fixedto the film formation chamber, the film formation chamber needs to be atan atmospheric pressure to supply the evaporation material to theevaporation source. Therefore, it takes time to evacuate the filmformation chamber for re-evaporation. When the setting chamber 707 isprovided, atmospheric pressure and vacuum can be switched only in thesetting chamber 707 while the vacuum is kept in the film formationchamber 700; thus, the evaporation material can be supplied in a shorttime.

Although the example of providing one film formation chamber with oneevaporation source is described here, one film formation chamber may beprovided with two or more evaporation sources.

In evaporation, the thick portion, that is, the top of the partition 11is in contact with the evaporation mask and functions to maintain adistance. When the partition 11 is arranged so as to surround the firstelectrode, evaporation onto a region below the mask where an opening isnot provided, for example, an adjacent pixel can be prevented. Note thatthe partition 11 is formed on the insulating film 18 to surround an endportion of each first electrode, and the first electrode is insulatedfrom an adjacent first electrode and prevented from short-circuiting. Inaddition, the thick portion, that is, the top of the partition 11overlaps with the opening reaching the electrode of the TFT.

Since an aperture ratio is decreased when the width of this partition 11is large, it is preferable to improve an aperture ratio and definitionby minimizing an upper surface shape of the partition. In addition, byoverlapping the layer 14 containing an organic compound with the thinportion of the partition 11, the first electrode formed below thepartition and a second electrode to be formed later can be effectivelyprevented from short-circuiting. In other words, a portion of the layer14 containing an organic compound which is overlapped with the partition11, that is, a portion which does not contribute to light emissionfunctions also as a part of the partition.

Next, the second electrode 15 serving as a cathode is formed over thelayer 14 containing an organic compound. An evaporation mask is usedalso when forming the second electrode 15. When an opening of theevaporation mask corresponds to an entire pixel portion, a structureformed in a portion other than the pixel portion maintains a distance tothe evaporation mask.

Through the above steps, a structure shown in FIG. 1C can be obtained.In addition, a resistance heating method which does not damage the TFT16 is preferable as a method for forming the layer 14 containing anorganic compound and the second electrode 15, and a coating method (suchas an ink-jet method or a spin coating method) can also be used.Further, the layer 14 containing an organic compound may be stacked witha film formed by a coating method and a film formed by an evaporationmethod. For example, after applying a poly(ethylenedioxythiophene)/poly(styrenesulfonic acid) aqueous solution (PEDOT/PSS),a polyaniline/camphor sulfonate aqueous solution (PANI/CSA), PTPDES,Et-PTPDEK, PPBA, or the like which functions as a hole injection layerby a spin coating method and baking the same, a light emitting layer, anelectron transport layer, or the like may be stacked by an evaporationmethod.

In FIG. 1C, a reference numeral 10 denotes a substrate; 11, a partition;12, a base insulating film; 13, a first electrode; 14, a layercontaining an organic compound; 15, a second electrode; 16, a TFT; 17, astacked layer of insulating films including a gate insulating film; 18,an insulating film; and 19, a wire such as a power supply line. Notethat in FIG. 1C, the first electrode 13 is formed to function as ananode of a light emitting element and the second electrode is formed tofunction as a cathode. However, there is no particular limitation, andthe first electrode can be formed to function as a cathode and thesecond electrode can be formed to function as an anode by appropriatelyselecting a material.

In addition, the present invention is not limited to the TFT structureof FIG. 1A, and a lightly doped drain (LDD) structure having an LDDregion between a channel formation region and a drain region (or asource region) may be employed if necessary. In this structure, a regionto which an impurity element is added at low concentration is providedbetween a channel formation region and a source or drain region which isformed by adding an impurity element at high concentration, and thisregion is referred to as an LDD region. Furthermore, a so-called GOLD(Gate-drain Overlapped LDD) structure, in which an LDD region isoverlapped with a gate electrode with a gate insulating film interposedtherebetween, may be employed.

In addition, although explanation is made here using an n-channel TFT,it is needless to say that a p-channel TFT can be formed by using animpurity element which imparts p-type conductivity instead of animpurity element which imparts n-type conductivity.

Furthermore, although an example is explained here using a top-gate TFT,the present invention can be applied regardless of a TFT structure. Forexample, the present invention can be applied to a bottom-gate (inversedstaggered) TFT or a forward staggered TFT.

In this specification, as a semiconductor layer serving as an activelayer of the TFT, a semiconductor film containing silicon as its maincomponent, a semiconductor film containing an organic material as itsmain component, or a semiconductor film containing metal oxide as itsmain component can be used. As the semiconductor film containing siliconas its main component, an amorphous semiconductor film, a semiconductorfilm including a crystalline structure, a compound semiconductor filmincluding an amorphous structure, or the like can be used. Specifically,as for the semiconductor film containing silicon as its main component,amorphous silicon, microcrystalline silicon, polycrystalline silicon, orthe like can be used. As the semiconductor film containing an organicmaterial as its main component, a semiconductor film containing, as itsmain component, a substance which includes a certain amount of carbon oran allotrope of carbon (excluding diamond) in combination with anotherelement can be used. Specifically, pentacene, tetracene, a thiophenoligomer derivative, a phenylene derivative, a phthalocyanine compound,a polyacetylene derivative, a polythiophene derivative, a cyaninepigment, or the like can be used. Further, as the semiconductor filmcontaining metal oxide as its main component, zinc oxide (ZnO); oxide ofzinc, gallium, and indium (In—Ga—Zn—O); or the like can be used.

Embodiment Mode 2

This embodiment mode describes an example of a structure which ispartially different from that of Embodiment Mode 1 with reference toFIG. 3.

Here, a structure in which one layer of the interlayer insulating filmin FIGS. 1A to 1C is reduced, specifically, a structure in which theinsulating film 18 shown in FIGS. 1A to 1C is not formed is described.Note that in FIG. 3, the same reference numeral is used to denote thesame portion as that in FIGS. 1A to 1C.

Similarly to Embodiment Mode 1, a TFT 16 is manufactured over asubstrate 10 having an insulating surface. Next, a first electrode 33serving as an anode is formed over a stacked layer 17 of insulatingfilms including a gate insulating film. The first electrode 33 is formedover the stacked layer 17 of insulating films including a gateinsulating film so as to be partially in contact with and overlappedwith an electrode electrically connected to a source region or a drainregion of the TFT.

Next, an insulating film is entirely formed by a coating method, andthen a partition 31 is formed using a photomask or a reticle providedwith an auxiliary pattern having a light intensity reduction functionmade of a diffraction grating pattern or a semi-transmissive film. Thepartition 31 includes a thick portion and a thin portion. In addition,the partition 31 is provided on the stacked layer 17 of insulating filmsincluding a gate insulating film, and is in contact with and covers awire 19 such as a power supply line.

Next, a layer 34 containing an organic compound is formed by anevaporation method. Although FIGS. 1A to 1C show an example in which thelayer 14 containing an organic compound is overlapped with the thinportion of the partition 11, FIG. 3 shows an example in which the layer34 containing an organic compound is overlapped also with the thickportion of the partition 31. The layer 34 containing an organic compoundis overlapped also with the thick portion of the partition 31 as shownin FIG. 3 because an evaporation mask is used of which the width of ashielding portion is smaller than that of the thick portion of thepartition 31 in a cross section taken perpendicularly to the substrateplane. In the present invention, the width of the shielding portion ofthe evaporation mask may be smaller than, the same as, or larger thanthe width of the partition. Further, by overlapping the layer 34containing an organic compound also with the thick portion of thepartition 31, the TFT formed below the partition and a second electrodeto be formed later can be effectively prevented from short-circuiting.

Next, a second electrode 15 serving as a cathode is formed over thelayer 34 containing an organic compound.

Through the above steps, the structure shown in FIG. 3 can be obtained.

Thus, the structure shown in FIG. 3 can be manufactured through fewersteps than those shown in FIGS. 1A to 1C.

This embodiment mode can be freely combined with Embodiment Mode 1.

Embodiment Mode 3

This embodiment mode describes an example of providing a partition in apixel portion where a plurality of light emitting elements is arranged(also referred to as a display region) and a structure arranged tosurround the pixel portion.

Here, an example of manufacturing a passive matrix light emitting deviceis described with reference to FIGS. 4A and 4B.

A first electrode 303 is formed over a first substrate 301, and apartition 302 is formed to cover an end portion of the first electrode303. In addition, a structure 304 is formed in the same step as thepartition 302. The partition 302 and the structure 304 have differentthicknesses. A cross-sectional view at this stage is shown in FIG. 4A.

Next, a layer 305 containing an organic compound is formed over thefirst electrode 303, and a second electrode 307 is formed thereover.Note that in forming the layer 305 containing an organic compound by anevaporation method, the structure 304 can prevent an evaporation maskand the first electrode 303 from being in contact with each other. Inaddition, the structure 304 can also prevent the evaporation mask andthe partition 302 from being in contact with each other.

Then, sealing is performed by attaching a second substrate 308 to thefirst substrate 301 with an adhesive layer 309.

As shown in FIG. 4B, the structure 304 arranged over the first substrate301 to surround a pixel portion 306 can maintain a distance between apair of substrates when sealing is performed using the second substrate308. In addition, the pixel portion can also be sealed by sealing aregion surrounded by the structure and the pair of substrates. In otherwords, the structure 304 can prevent the entry of an impurity andmoisture from the outside.

The partition 302 and the structure 304 are formed in the same stepusing a photomask or a reticle including a diffraction grating patternor a semi-transmissive portion.

In the case of manufacturing an active matrix light emitting device, apartition which is provided in a pixel portion where a plurality oflight emitting elements is arranged (also referred to a display region)and a structure which is arranged to surround the pixel portion may besimilarly formed.

In the case of manufacturing an active matrix light emitting device, apart of a driver circuit can also be formed with a TFT in the same stepas a TFT arranged in a pixel. In that case, the driver circuit isarranged around the pixel portion. In addition, the structure may beformed in a position overlapped with the driver circuit.

This embodiment mode can be freely combined with Embodiment Mode 1 or 2.

For example, by forming the partition into a shape which spreads towardthe bottom and forming a part of the partition to have the samethickness as the structure, a distance between the pair of substratescan be maintained with both the partition and the structure. In the caseof providing a partition having such an upper surface shape as tosurround one pixel, sealing can be performed by sealing one pixel withthe second substrate and the partition, and sealing can be performed byfurther sealing the periphery with the structure. By performing sealingtwice as described above, a light emitting device with high reliabilitycan be achieved. When the light emitting device is subjected to externalimpact, the force of the impact can be dispersed because the pair ofsubstrates is supported with the partition and the structure. Therefore,a durable light emitting device can be provided.

Embodiment Mode 4

This embodiment mode describes steps of forming a TFT, entirely forminga photosensitive resin film, forming a partition using a photomaskprovided with an auxiliary pattern having a light intensity reductionfunction made of a semi-transmissive film, up to the completion of alight emitting device.

First, over a substrate 100 having an insulating surface, a base film101 a is formed using a silicon nitride oxide (SiNO) film with athickness of 10 nm to 200 nm (preferably, 50 nm to 100 nm) and a basefilm 101 b is stacked thereover using a silicon oxynitride (SiON) filmwith a thickness of 50 nm to 200 nm (preferably, 100 nm to 150 nm) by asputtering method, a PVD (Physical Vapor Deposition) method, a CVD(Chemical Vapor Deposition) method such as a low pressure CVD (LPCVD)method or a plasma CVD method, or the like. In this embodiment mode, thebase film 101 a and the base film 101 b are formed using a plasma CVDmethod. As the substrate 100, a glass substrate, a quartz substrate, ora silicon substrate, a metal substrate, or a stainless steel substrateprovided with an insulating film on the surface may be used. Inaddition, a plastic substrate having heat resistance sufficient towithstand a processing temperature of this embodiment mode may be used,or a flexible film-like substrate may be used. As the plastic substrate,a substrate made of PET (polyethylene terephthalate), PEN(polyethylenenaphthalate), or PES (polyethersulfone) can be used, and asthe flexible substrate, a synthetic resin such as acrylic can be used.

The base film can be formed using silicon oxide, silicon nitride,silicon oxynitride, silicon nitride oxide, or the like and it may haveeither a single-layer structure or a stacked structure of two or morelayers. In this specification, silicon oxynitride refers to a substancehaving a higher composition ratio of oxygen than that of nitrogen, andcan also be referred to as silicon oxide containing nitrogen. Similarly,silicon nitride oxide refers to a substance having a higher compositionratio of nitrogen than that of oxygen, and can also be referred to assilicon nitride containing oxygen. In this embodiment mode, over thesubstrate, a silicon nitride oxide film is formed with a thickness of 50nm using SiH₄, NH₃, N₂O, N₂, and H₂ as a reaction gas, and a siliconoxynitride film is formed with a thickness of 100 nm using SiH₄ and N₂Oas a reaction gas. The thickness of the silicon nitride oxide film maybe 140 nm and the thickness of the silicon oxynitride film to be stackedmay be 100 nm.

Next, a semiconductor film is formed over the base film. Thesemiconductor film may be formed with a thickness of 25 nm to 200 nm(preferably, 30 nm to 150 nm) by a known method (such as a sputteringmethod, an LPCVD method, or a plasma CVD method). In this embodimentmode, a crystalline semiconductor film formed by crystallizing anamorphous semiconductor film with a laser beam is preferably used. Inthe case of using a crystalline semiconductor film, the crystallinesemiconductor film may be formed using a known method (such as a lasercrystallization method, a thermal crystallization method, or a thermalcrystallization method using an element which promotes crystallizationsuch as nickel).

A crystal with a large grain size can be obtained by irradiation withlaser light of the second to fourth harmonic of a fundamental wave usinga solid-state laser capable of continuous oscillation. Typically, it isdesirable that the second harmonic (532 nm) or the third harmonic (355nm) of a Nd:YVO₄ laser (fundamental wave: 1064 nm) be used.Specifically, laser light with an output of several W or more isobtained by converting laser light emitted from a continuous-wave YVO₄laser into a harmonic by a nonlinear optical element. Then, it ispreferable to shape the laser light into a rectangular or ellipticalshape on an irradiation surface by an optical system and irradiate thesemiconductor film with the laser light. A power density at this timeneeds to be approximately 0.001 MW/cm² to 100 MW/cm² (preferably, 0.1MW/cm² to 10 MW/cm²). Subsequently, irradiation is performed with a scanrate of approximately 0.5 cm/sec to 2000 cm/sec (preferably, 10 cm/secto 200 cm/sec).

The beam shape of the laser is preferably linear. Accordingly,throughput can be improved. Further, the semiconductor film ispreferably irradiated with the laser with an incident angle θ(0°<θ<90°). This is because laser interference can be prevented.

Laser irradiation can be performed by moving such a laser relative tothe semiconductor film. In addition, a marker can be formed to overlapbeams with accuracy or to control a laser irradiation start position anda laser irradiation termination position in laser irradiation. Themarker may be formed over the substrate at the same time as theamorphous semiconductor film.

As the laser, a continuous-wave or pulsed gas laser, solid-state laser,copper vapor laser, gold vapor laser, or the like can be used. As thegas laser, an excimer laser, an Ar laser, a Kr laser, a He—Cd laser, orthe like can be used, and as the solid-state laser, a YAG laser, a YVO₄laser, a YLF laser, a YAlO₃ laser, a Y₂O₃ laser, a glass laser, a rubylaser, an alexandrite laser, a Ti:sapphire laser, or the like can beused.

As a material for forming the semiconductor film, an amorphoussemiconductor (hereinafter also referred to as an “AS”) manufactured bya vapor phase growth method or a sputtering method using a semiconductormaterial gas typified by silane or germane; a polycrystallinesemiconductor that is formed by crystallizing the amorphoussemiconductor by utilizing light energy or thermal energy; asemiamorphous (also referred to as microcrystalline or microcrystal)semiconductor (hereinafter also referred to as a “SAS”); or the like canbe used.

In addition, laser crystallization may be performed using a pulsed laserbeam with a repetition rate of 0.5 MHz or more and using a frequencyband which is much higher than a generally used frequency band, severaltens to several hundreds Hz. It is said that the time required for thesemiconductor film irradiated with pulsed laser light to solidifycompletely is several tens nsec to several hundreds nsec. By using theabove frequency band, the semiconductor film can be irradiated withpulsed laser light after being melted by the previous laser light andbefore being solidified. Accordingly, the interface between the solidphase and the liquid phase can be moved continuously in thesemiconductor film; therefore, a semiconductor film having crystalgrains grown continuously in the scanning direction is formed.Specifically, a cluster of crystal grains of which width in a scanningdirection is 10 μm to 30 μm and width in a direction perpendicular tothe scanning direction is approximately 1 μm to 5 μm can be formed. Byforming crystal grains of a single crystal which extend long along thescanning direction, a semiconductor film can be formed in which crystalgrain boundaries hardly exist at least in a channel direction of a thinfilm transistor.

The laser light irradiation may be performed in an inert gas atmospheresuch as a noble gas or nitrogen. This can suppress roughness of asemiconductor surface caused by the laser light irradiation and suppressvariations in the threshold caused by variations in interface statedensity.

Crystallization of the amorphous semiconductor film may be performed bya combination of heat treatment and laser light irradiation, or byindependently performing heat treatment or laser light irradiationplural times.

In this embodiment mode, a crystalline semiconductor film is formed byforming an amorphous semiconductor film over the base film 101 b andcrystallizing the amorphous semiconductor film. For the amorphoussemiconductor film, amorphous silicon formed from a reaction gas of SiH₄and H₂ is used. In this embodiment mode, the base film 101 a, the basefilm 101 b, and the amorphous semiconductor film are formed continuouslyin the same chamber at the same temperature of 330° C. while keeping avacuum with reactive gases changed. Next, the amorphous semiconductorfilm is irradiated with laser light, specifically, a fundamental waveemitted from a laser oscillator with a repetition rate of 10 MHz ormore, thereby forming the crystalline semiconductor film. A peak outputof the laser light at this time is assumed to be in the range of 1GW/cm² to 1 TW/cm². A cross-sectional view at this stage is shown inFIG. 5A.

The crystalline semiconductor film obtained as described above may bedoped with a slight amount of an impurity element (boron or phosphorus)to control a threshold voltage of the thin film transistor. This dopingwith an impurity element may be performed to the amorphous semiconductorfilm before the crystallization step. When the amorphous semiconductorfilm is doped with an impurity element, activation of the impurityelement can be performed by subsequent heat treatment forcrystallization. In addition, defects and the like caused by doping canbe improved.

Next, the crystalline semiconductor film 102 is selectively etched usinga mask. In this embodiment mode, after removing an oxide film formed onthe crystalline semiconductor film 102, another oxide film is formed.Then, a photomask is formed, and a semiconductor layer 103, asemiconductor layer 104, a semiconductor layer 105, and a semiconductorlayer 106 are formed by a patterning process using a photolithographymethod.

Subsequently, the oxide film on the semiconductor layer is removed, anda gate insulating layer 107 is formed to cover the semiconductor layer103, the semiconductor layer 104, the semiconductor layer 105, and thesemiconductor layer 106.

The gate insulating layer 107 is formed using an insulating filmcontaining silicon with a thickness of 10 nm to 150 nm by a plasma CVDmethod, a sputtering method, or the like. The gate insulating layer 107may be formed of a known material such as an oxide material or nitridematerial of silicon typified by silicon nitride, silicon oxide, siliconoxynitride, or silicon nitride oxide, and it may have either asingle-layer structure or a stacked structure. In this embodiment mode,the gate insulating layer is formed to have a three-layer structure of asilicon nitride film, a silicon oxide film, and a silicon nitride film.Alternatively, a single layer of a silicon oxynitride film or a stackedlayer of two layers may be used. Preferably, a silicon nitride filmhaving dense film quality is used. Furthermore, a thin silicon oxidefilm with a thickness of 1 nm to 100 nm, preferably, 1 nm to 10 nm, morepreferably, 2 nm to 5 nm may be formed between the semiconductor layerand the gate insulating layer. The thin silicon oxide film can be formedby oxidizing the surface of a semiconductor region using a GRTA method,an LRTA method, or the like to form a thermal oxidation film.

Next, a first conductive film 108 with a thickness of 20 nm to 100 nmand a second conductive film 109 with a thickness of 100 nm to 400 nm,which are used as a gate electrode layer, are stacked over the gateinsulating layer 107 (see FIG. 5B).

The first conductive film 108 and the second conductive film 109 can beformed by a known method such as a sputtering method, an evaporationmethod, a CVD method, or the like. Each of the first conductive film 108and the second conductive film 109 may be formed using an elementselected from tantalum (Ta), tungsten (W), titanium (Ti), molybdenum(Mo), aluminum (Al), copper, (Cu), chromium (Cr), and neodymium (Nd), oran alloy material or compound material containing the above element asits main component. In addition, a semiconductor film typified by apolycrystalline silicon film doped with an impurity element such asphosphorus, or an AgPdCu alloy may be used for the first conductive film108 and the second conductive film 109. In addition, the gate electrodelayer is not limited to the two-layer structure and it may have athree-layer structure in which a tungsten film with a thickness of 50 nmas a first conductive film, an alloy film of aluminum and silicon(Al—Si) with a thickness of 500 nm as a second conductive film, and atitanium nitride film with a thickness of 30 nm as a third conductivefilm are sequentially stacked. In the case of the three-layer structure,tungsten nitride may be used in place of tungsten of the firstconductive film, an alloy film of aluminum and titanium (Al—Ti) may beused in place of the alloy film of aluminum and silicon (Al—Si) of thesecond conductive film, and a titanium film may be used in place of thetitanium nitride film of the third conductive film. Alternatively, thegate electrode layer may be a single-layer structure. In this embodimentmode, a tantalum nitride (TaN) film is formed as the first conductivefilm 108 with a thickness of 30 nm, and a tungsten (W) film is formed asthe second conductive film 109 with a thickness of 370 nm.

Next, a resist mask is formed using a photomask or a reticle providedwith an auxiliary pattern having a light intensity reduction functionmade of a diffraction grating pattern or a semi-transmissive film, andthe first conductive film 108 and the second conductive film 109 areselectively etched to form a first gate electrode layer, a conductivelayer, and a second gate electrode layer so as to have a tapered shape.The resist mask includes a thick portion and a thin portion, and isformed so that a portion in which a channel formation region is to beformed is overlapped with the thick portion of the resist mask. After anelectrode or a wire with a cross-sectional shape which spreads towardthe bottom is obtained, the resist mask is removed.

Through the above steps, a gate electrode layer 117 including a firstgate electrode layer 121 and a second gate electrode layer 131, and agate electrode layer 118 including a first gate electrode layer 122 anda second gate electrode layer 132 can be formed in a peripheral drivercircuit region 204; a gate electrode layer 127 including a first gateelectrode layer 124 and a second gate electrode layer 134, a gateelectrode layer 128 including a first gate electrode layer 125 and asecond gate electrode layer 135, and a gate electrode layer 129including a first gate electrode layer 126 and a second gate electrodelayer 136 can be formed in a pixel region 206; and a conductive layer130 including a conductive layer 123 and a conductive layer 133 can beformed in a connection region 205 (see FIG. 5C). Although the gateelectrode layers are formed by dry etching in this embodiment mode, wetetching may be employed.

Note that through the etching step in forming the gate electrode layers,the gate insulating layer 107 may be etched to a certain extent and thethickness thereof may be decreased (so-called film reduction).

Subsequently, an impurity element 151 which imparts n-type conductivityis added using the gate electrode layer 117, the gate electrode layer118, the gate electrode layer 127, the gate electrode layer 128, thegate electrode layer 129, and the conductive layer 130 as masks to forma first n-type impurity region 140 a, a first n-type impurity region 140b, a first n-type impurity region 141 a, a first n-type impurity region141 b, a first n-type impurity region 142 a, a first n-type impurityregion 142 b, a first n-type impurity region 142 c, a first n-typeimpurity region 143 a, and a first n-type impurity region 143 b (seeFIG. 6A). Here, with the use of phosphine (PH₃) as a doping gasincluding an impurity element, the impurity element which imparts n-typeconductivity is added so as to be contained in the first n-type impurityregion 140 a, the first n-type impurity region 140 b, the first n-typeimpurity region 141 a, the first n-type impurity region 141 b, the firstn-type impurity region 142 a, the first n-type impurity region 142 b,the first n-type impurity region 142 c, the first n-type impurity region143 a, and the first n-type impurity region 143 b at a concentration ofapproximately 1×10¹⁷/cm³ to 5×10¹⁸/cm³.

Next, a mask 153 a, a mask 153 b, a mask 153 c, and a mask 153 d areformed to cover the semiconductor layer 103, a part of the semiconductorlayer 105, and the semiconductor layer 106. An impurity element 152which imparts n-type conductivity is added using the mask 153 a, themask 153 b, the mask 153 c, the mask 153 d, and the second gateelectrode layer 132 as masks to form a second n-type impurity region 144a, a second n-type impurity region 144 b, a third n-type impurity region145 a, a third n-type impurity region 145 b, a second n-type impurityregion 147 a, a second n-type impurity region 147 b, a second n-typeimpurity region 147 c, a third n-type impurity region 148 a, a thirdn-type impurity region 148 b, a third n-type impurity region 148 c, anda third n-type impurity region 148 d (see FIG. 6B). Here, the impurityelement which imparts n-type conductivity is added so as to be containedin the second n-type impurity region 144 a and the second n-typeimpurity region 144 b at a concentration of approximately 5×10¹⁹/cm³ to5×10²⁰/cm³. The third n-type impurity region 145 a and the third n-typeimpurity region 145 b are formed to contain the impurity element whichimparts n-type conductivity at the same concentration as or at aslightly higher concentration than the third n-type impurity region 148a, the third n-type impurity region 148 b, the third n-type impurityregion 148 c, and the third n-type impurity region 148 d. In addition, achannel formation region 146 is formed in the semiconductor layer 104,and a channel formation region 149 a and a channel formation region 149b are formed in the semiconductor layer 105.

Each of the second n-type impurity region 144 a, the second n-typeimpurity region 144 b, the second n-type impurity region 147 a, thesecond n-type impurity region 147 b, and the second n-type impurityregion 147 c is a high-concentration n-type impurity region andfunctions as a source or a drain. On the other hand, each of the thirdn-type impurity region 145 a, the third n-type impurity region 145 b,the third n-type impurity region 148 a, the third n-type impurity region148 b, the third n-type impurity region 148 c, and the third n-typeimpurity region 148 d is a low-concentration impurity region andfunctions as an LDD (Lightly Doped Drain) region. Each of the n-typeimpurity region 145 a and the n-type impurity region 145 b is an Lovregion because it is covered with the first gate electrode layer 122with the gate insulating layer 107 interposed therebetween, and canrelieve an electric field in the vicinity of a drain and suppressdegradation of on-state current due to hot carriers. As a result, a thinfilm transistor which can operate at high speed can be formed. On theother hand, since each of the third n-type impurity region 148 a, thethird n-type impurity region 148 b, the third n-type impurity region 148c, and the third n-type impurity region 148 d is formed in an Loffregion which is not covered with the gate electrode layer 127 or thegate electrode layer 128, it has the effect of reducing off-statecurrent as well as relieving an electric field in the vicinity of adrain and preventing deterioration due to hot carrier injection. As aresult, a semiconductor device which has high reliability and consumesless power can be manufactured.

Note that in this embodiment mode, a region where the impurity region isoverlapped with the gate electrode layer with the gate insulating layerinterposed therebetween is referred to as the Lov region, and a regionwhere the impurity region is not overlapped with the gate electrodelayer with the gate insulating layer interposed therebetween is referredto as the Loff region.

Next, the mask 153 a, the mask 153 b, the mask 153 c, and the mask 153 dare removed, and a mask 155 a and a mask 155 b are formed to cover thesemiconductor layer 104 and the semiconductor layer 105. An impurityelement 154 which imparts p-type conductivity is added using the mask155 a, the mask 155 b, the gate electrode layer 117, and the gateelectrode layer 129 as masks to form a first p-type impurity region 160a, a first p-type impurity region 160 b, a first p-type impurity region163 a, a first p-type impurity region 163 b, a second p-type impurityregion 161 a, a second p-type impurity region 161 b, a second p-typeimpurity region 164 a, and a second p-type impurity region 164 b (seeFIG. 6C). In this embodiment mode, boron (B) is used as the impurityelement. Here, the impurity element which imparts p-type conductivity isadded so as to be contained in the first p-type impurity region 160 a,the first p-type impurity region 160 b, the first p-type impurity region163 a, the first p-type impurity region 163 b, the second p-typeimpurity region 161 a, the second p-type impurity region 161 b, thesecond p-type impurity region 164 a, and the second p-type impurityregion 164 b at a concentration of approximately 1×10²⁰/cm³ to5×10²¹/cm³. In this embodiment mode, the second p-type impurity region161 a, the second p-type impurity region 161 b, the second p-typeimpurity region 164 a, and the second p-type impurity region 164 breflect the shapes of the gate electrode layer 117 and the gateelectrode layer 129, and are formed in a self-aligned manner so as tohave a lower concentration than that of the first p-type impurity region160 a, the first p-type impurity region 160 b, the first p-type impurityregion 163 a, and the first p-type impurity region 163 b. In addition, achannel formation region 162 and a channel formation region 165 areformed in the semiconductor layer 103 and the semiconductor layer 106,respectively.

Next, the mask 155 a and the mask 155 b are removed by O₂ ashing or aresist peeling solution, and an oxide film is also removed.

Next, heat treatment, intense light irradiation, or laser lightirradiation is performed to activate the impurity element. This canrepair plasma damage to the gate insulating layer and the interfacebetween the gate insulating layer and the semiconductor layer at thesame time as activation.

Subsequently, an interlayer insulating layer is formed to cover the gateelectrode layers and the gate insulating layer. In this embodiment mode,the interlayer insulating layer is formed to have a stacked structure ofan insulating film 167 and an insulating film 168 (see FIG. 7A). Thestacked structure is formed by forming a silicon nitride oxide film witha thickness of 200 nm as the insulating film 167 and forming a siliconoxynitride film with a thickness of 800 nm as the insulating film 168.Alternatively, the interlayer insulating layer may be formed to have athree-layer structure by forming a silicon oxynitride film with athickness of 30 nm, forming a silicon nitride oxide film with athickness of 140 nm, forming a silicon oxynitride film with a thicknessof 800 nm to cover the gate electrode layers and the gate insulatinglayer. In this embodiment mode, the insulating film 167 and theinsulating film 168 are continuously formed using a plasma CVD method ina similar manner to the base film. The insulating film 167 and theinsulating film 168 are not limited to a silicon nitride film, and maybe a silicon nitride oxide film, a silicon oxynitride film, or a siliconoxide film, or another insulating film containing silicon used as asingle layer or a stacked structure of three or more layers.

Next, heat treatment is performed in a nitrogen atmosphere at 300° C. to550° C. for 1 to 12 hours to hydrogenate the semiconductor layer.Preferably, it is performed at 400° C. to 500° C. This step is a step ofterminating dangling bonds of the semiconductor layer with hydrogencontained in the insulating film 167 that is the interlayer insulatinglayer. In this embodiment mode, heat treatment is performed at 410° C.

Next, contact holes (openings) are formed in the insulating film 167,the insulating film 168, and the gate insulating layer 107 using a maskmade of a resist so as to reach the semiconductor layers. Etching may beperformed once or a plurality of times depending on a selection ratio ofa material to be used.

Next, a conductive film is formed to cover the openings, and theconductive film is etched to form a source or drain electrode layer 169a, a source or drain electrode layer 169 b, a source or drain electrodelayer 170 a, a source or drain electrode layer 170 b, a source or drainelectrode layer 171 a, a source or drain electrode layer 171 b, a sourceor drain electrode layer 172 a, a source or drain electrode layer 172 b,and a wire layer 156 each of which is electrically connected to a partof the source region or the drain region. The source or drain electrodelayer can be formed by forming a conductive film by a PVD method, a CVDmethod, an evaporation method, or the like and etching the conductivefilm into a desired shape. In addition, a conductive layer can beselectively formed in a predetermined position by a droplet dischargemethod, a printing method, an electrolytic plating method, or the like.Furthermore, a reflow method or a damascene method may be used. Thesource or drain electrode layer is formed using metal such as Ag, Au,Cu, Ni, Pt, Pd, Ir, Rh, W, Al, Ta, Mo, Cd, Zn, Fe, Ti, Zr, or Ba or analloy or metal nitride thereof. In addition, a conductive materialincluding Si or Ge may be used. In addition, it may have a stackedstructure thereof. In this embodiment mode, a titanium (Ti) film isformed with a thickness of 100 nm, an alloy film of aluminum and silicon(Al—Si) is formed with a thickness of 700 nm, and a titanium (Ti) filmis formed with a thickness of 200 nm, which are selectively etched intoa desired shape.

Through the above steps, an active matrix substrate can be manufacturedwhich includes a p-channel thin film transistor 173 having a p-typeimpurity region in the Lov region and an n-channel thin film transistor174 having an n-type impurity region in the Lov region in the peripheraldriver circuit region 204, a conductive layer 177 in the connectionregion, and a multi-channel n-channel thin film transistor 175 having ann-type impurity region in a Loff region and a p-channel thin filmtransistor 176 having a p-type impurity region in a Lov region in thepixel region 206 (see FIG. 7B).

Next, an insulating film 180 and an insulating film 181 are formed as asecond interlayer insulating layer (see FIG. 8A). FIGS. 8A to 8C show amanufacturing process for a display device, in which a reference numeral201 denotes a separation region for separation by scribing; 202, anexternal terminal connection region which is an attachment portion of anFPC; 203, a wire region which is a lead wire region of a peripheralportion; 204, a peripheral driver circuit region; 205, a connectionregion; and 206, a pixel region. In the wire region 203, a wire 179 aand a wire 179 b are provided, and in the external terminal connectionregion 202, a terminal electrode layer 178 connected to an externalterminal is provided.

The insulating film 180 and the insulating film 181 can be formed of amaterial selected from substances including an inorganic insulatingmaterial such as silicon oxide, silicon nitride, silicon oxynitride,silicon nitride oxide, aluminum nitride (AlN), aluminum oxynitride(AlON), aluminum nitride oxide (AlNO) having a higher content ofnitrogen than that of oxygen, aluminum oxide, diamond-like carbon (DLC),a nitrogen-containing carbon film (CN), PSG (phosphosilicate glass),BPSG (borophosphosilicate glass), an alumina film, and polysilazane.Alternatively, a siloxane resin may be used. Note that the siloxaneresin corresponds to a resin having Si—O—Si bonds. Siloxane has askeleton structure formed from a bond of silicon (Si) and oxygen (O). Asa substituent, an organic group containing at least hydrogen (forexample, an alkyl group or aromatic hydrocarbon) is used. A fluoro groupmay be used as the substituent. Alternatively, an organic groupcontaining at least hydrogen and a fluoro group may be used as thesubstituent. Furthermore, an organic insulating material may be used; anorganic material may be either photosensitive or non-photosensitive; andpolyimide, acrylic, polyamide, polyimide amide, a resist,benzocyclobutene, or a low-dielectric constant organic insulatingmaterial can be used.

Subsequently, openings 182 and 183 are formed in the insulating film 180and the insulating film 181 which are the second interlayer insulatinglayer as shown in FIG. 8B. In the connection region 205, the wire region203, the external terminal connection region 202, the separation region201, and the like, a large area of the insulating film 180 and theinsulating film 181 needs to be etched. However, in the pixel region206, an opening area is significantly smaller and more minute than thatin the connection region 205 or the like. Therefore, a photolithographystep for forming an opening in the pixel region and a photolithographystep for forming an opening in the connection region are performedseparately.

Then, a minute opening 184, that is, a contact hole is formed in theinsulating film 180 and the insulating film 181 in the pixel region 206as shown in FIG. 8C.

This embodiment mode explains the case of etching the insulating film180 and the insulating film 181 using a mask which covers the connectionregion 205, the wire region 203, the external terminal connection region202, the separation region 201, and the peripheral driver circuit region204 and is provided with a predetermined opening in the pixel region206. However, the present invention is not limited thereto. For example,since the opening in the connection region 205 has large area, theamount to be etched is large. Such a large-area opening may be formed byperforming etching a plurality of times.

Next, a first electrode layer 185 (also referred to as a pixel electrodelayer) is formed to be in contact with the source or drain electrodelayer 172 a as shown in FIG. 9A. The first electrode layer functions asan anode or a cathode, and may be formed using a film containing as itsmain component an element selected from Ti, Ni, W, Cr, Pt, Zn, Sn, In,and Mo, TiN, TiSi_(X)N_(Y), WSi_(X), WN_(X), WSi_(X)N_(Y), NbN, or analloy or compound material containing the above element as its maincomponent or stacked films thereof with a total thickness of 100 nm to800 nm.

In this embodiment mode, a structure in which a light emitting elementis used as a display element and light emitted from the light emittingelement is extracted from the first electrode layer 185 side isemployed; therefore, the first electrode layer 185 has a lighttransmitting property. A transparent conductive film is formed andetched into a desired shape, thereby forming the first electrode layer185. For the first electrode layer 185 used in the present invention,indium tin oxide containing silicon oxide (hereinafter referred to as“ITSO”), zinc oxide, tin oxide, indium oxide, or the like may be used.Alternatively, a transparent conductive film such as an alloy of indiumoxide and zinc oxide in which indium oxide is mixed with zinc oxide(ZnO) of 2 wt % to 20 wt % can be used. In addition to the transparentconductive film, a titanium nitride film or a titanium film may be usedfor the first electrode layer 185. In this case, after forming thetransparent conductive film, a titanium nitride film or a titanium filmis formed with such a thickness as to transmit light (preferably,approximately 5 nm to 30 nm). In this embodiment mode, ITSO using indiumtin oxide and silicon oxide is used for the first electrode layer 185.

FIG. 11 shows an example of a top view of the pixel region at the stagewhere the first electrode layer 185 is formed. In FIG. 11, one pixelincludes a TFT 501, a TFT 502, a capacitor element 504, a firstelectrode layer 185, a gate wire layer 506, a source and drain wirelayer 505, and a power supply line 507.

Next, heat treatment may be performed after forming the first electrodelayer 185. Through this heat treatment, moisture included in the firstelectrode layer 185 is released. Therefore, degasification or the likeis not caused in the first electrode layer 185. Even when a lightemitting material which is easily deteriorated by moisture is formedover the first electrode layer, the light emitting material is notdeteriorated; thus, a highly reliable display device can bemanufactured. Since ITSO is used for the first electrode layer 185 inthis embodiment mode, it remains amorphous even when baked unlike ITO(alloy of indium oxide and zinc oxide) which is crystallized when baked.Accordingly, ITSO has higher planarity than ITO and short-circuit with acathode is not easily generated even when the layer containing anorganic compound is thin.

Subsequently, a partition 186 made of an insulating material is formedto cover an end portion of the first electrode layer 185 and the sourceor drain electrode layer (see FIG. 9B). The partition 186 is formedusing a photomask or a reticle provided with an auxiliary pattern havinga light reduction function made of a diffraction grating pattern or asemi-transmissive film. In addition, the partition 186 has across-sectional shape including a plurality of thick portions and has astep on its side. This partition 186 can be obtained by a manufacturingmethod according to Embodiment Mode 1.

In order to perform a full color display, electroluminescent layers foremitting light of RGB need to be formed separately when forming anelectroluminescent layer over the first electrode layer. Therefore, whenforming electroluminescent layers of the other colors, the pixelelectrode layer (first electrode layer) is covered with an evaporationmask. The evaporation mask may be a film formed of a metal material orthe like. At this time, the evaporation mask is provided over thepartition 186 and supported with the thick portions of the partition186. By providing the partition 186 with the thick portion, a defectiveshape of the first electrode layer due to a mask can be prevented, whichleads to manufacturing of a display device with high reliability andhigh image quality without the first electrode layer causing defectivelight emission and defective display.

In addition, an insulator (insulating layer) 187 a and an insulator(insulating layer) 187 b are formed in the external terminal connectionregion 202 in the same step as the partition 186.

In the connection region 205, the partition 186 is formed to cover endportions of the insulating film 180 and the insulating film 181 facingthe opening 182. Since the end portions of the insulating film 180 andthe insulating film 181 are processed to have steep steps by selectiveetching, coverage of a second electrode layer 189 to be stackedthereover is poor. Therefore, as in the present invention, steps aroundthe openings are covered with the partition 186 to smooth the steps,thereby improving the coverage of the second electrode layer 189 to bestacked. In the connection region 205, a wire layer formed of the samematerial and in the same step as the second electrode layer iselectrically connected to the wire layer 156. Although the secondelectrode layer 189 is in contact with and electrically connected to thewire layer 156 in this embodiment mode, it may be electrically connectedthrough another wire.

Next, an electroluminescent layer 188 is formed over the first electrodelayer 185. Note that, although FIG. 10 shows only one pixel, respectiveelectroluminescent layers corresponding to colors of R (red), G (green),and B (blue) are separately formed in this embodiment mode. In thisembodiment mode, for the electroluminescent layer 188, each materialemitting light of R (red), G (green), or B (blue) is selectively formedby an evaporation method using an evaporation mask.

Next, the second electrode layer 189 made of a conductive film is formedover the electroluminescent layer 188. For the second electrode layer189, a material having a low work function (Al, Ag, Li, Ca, an alloy ora compound thereof, MgAg, MgIn, AlLi, CaF₂, or calcium nitride) may beused. Thus, a light emitting element 190 including the first electrodelayer 185, the electroluminescent layer 188, and the second electrodelayer 189 is formed.

In the display device of this embodiment mode shown in FIG. 10, lightemitted from the light emitting element 190 is extracted from the firstelectrode layer 185 side to a direction indicated by an arrow in FIG.10.

It is effective to provide a passivation film 191 so as to cover thesecond electrode layer 189. As the passivation film 191, a single layeror a stacked layer of an insulating film formed of silicon nitride,silicon oxide, silicon oxynitride (SiON), silicon nitride oxide (SiNO),aluminum nitride (AlN), aluminum oxynitride (AlON), aluminum nitrideoxide (AlNO) having a higher content of nitrogen than that of oxygen,diamond-like carbon (DLC), or a nitrogen-containing carbon film (CN) canbe used. Alternatively, a siloxane resin material may be used.

Subsequently, the light emitting element is sealed by fixing thesubstrate 100 over which the light emitting element 190 is formed and asealing substrate 195 with a sealant 192 (see FIG. 10).

Note that a region surrounded by the sealant may be filled with a filleror an adhesive tape, and nitrogen may be contained by sealing the regionin a nitrogen atmosphere. Since bottom emission is employed in thisembodiment mode, the filler does not need to have a light transmittingproperty. However, in the case of employing a structure in which lightis transmitted and extracted through the filler, the filler needs tohave a light transmitting property. Typically, a visible light curing,ultraviolet curing, or thermosetting epoxy resin may be used. Throughthe above steps, a display device having a display function with the useof a light emitting element in this embodiment mode is completed.Alternatively, the filler can be dropped in a liquid state andencapsulated in the display device.

In addition, a desiccant may be provided in a panel to preventdeterioration of the light emitting element by moisture.

Next, in the external terminal connection region 202, an FPC 194 isconnected to the terminal electrode layer 178 with an anisotropicconductive layer 196 and electrically connected to the outside.

In the display device of the present invention, a driving method forimage display is not particularly limited, and for example, a dotsequential driving method, a line sequential driving method, an areasequential driving method, or the like may be used. Typically, the linesequential driving method is used, and a time division gray scaledriving method or an area gray scale driving method may be appropriatelyused. Further, a video signal inputted to the source line of the displaydevice may be either an analog signal or a digital signal. The drivercircuit and the like may be appropriately designed in accordance withthe video signal.

Furthermore, in a display device using a digital video signal, a videosignal inputted to a pixel is classified into a video signal at aconstant voltage (CV) and a video signal at a constant current (CC). Thevideo signal at a constant voltage (CV) is further classified into avideo signal with a constant voltage applied to a light emitting element(CVCV) and a video signal with a constant current applied to a lightemitting element (CVCC). In addition, the video signal at a constantcurrent (CC) is classified into a video signal with a constant voltageapplied to a light emitting element (CCCV) and a video signal with aconstant current applied to a light emitting element (CCCC).

By using the present invention, a highly reliable display device can bemanufactured through a simplified process. Therefore, a display devicewith high definition and high image quality can be manufactured at lowcost with high yield.

This embodiment mode can be freely combined with any one of EmbodimentModes 1 to 3.

Embodiment Mode 5

A television device can be completed by using the light emitting deviceformed in accordance with the present invention. As for the displaypanel, there are a case in which only a pixel portion is formed and ascan line driver circuit and a signal line driver circuit are mounted bya TAB method; a case in which a scan line driver circuit and a signalline driver circuit are mounted by a COG method; a case in which a TFTis formed, a pixel portion and a scan line driver circuit are formedover a substrate, and a signal line driver circuit is separately mountedas a driver IC; a case in which a pixel portion, a signal line drivercircuit, and a scan line driver circuit are integrated with a substrate;and the like. The display panel may have any structure.

As another external circuit, a video signal amplifier circuit whichamplifies a video signal among signals received by a tuner, a videosignal processing circuit which converts the signals outputted from thevideo signal amplifier circuit into color signals corresponding torespective colors of red, green, and blue, a control circuit whichconverts the video signal into an input specification of the driver IC,and the like are provided on an input side of the video signal. Thecontrol circuit outputs signals to both a scan line side and a signalline side. In the case of digital driving, a signal dividing circuit maybe provided on the signal line side and an input digital signal may bedivided into m pieces and supplied.

An audio signal among the signals received by the tuner is sent to anaudio signal amplifier circuit and an output thereof is supplied to aspeaker through an audio signal processing circuit. A control circuitreceives control information of a receiving station (receptionfrequency) or sound volume from an input portion and transmits signalsto the tuner and the audio signal processing circuit.

A television device can be completed by incorporating a display moduleinto a chassis as shown in FIGS. 12A and 12B. A display panel providedwith components up to an FPC is also referred to as a display module. Amain screen 2003 is formed by using the display module, and a speakerportion 2009, an operation switch, and the like are provided as itsaccessory equipment. Thus, a television device can be completed inaccordance with the present invention.

In addition, reflected light of light entering from outside may beblocked by using a retardation film or a polarizing plate. In the caseof a top emission display device, an insulating layer serving as apartition may be colored and used as a black matrix. This partition canbe formed by a droplet discharge method or the like. Carbon black or thelike may be mixed into a black resin of a pigment material or a resinmaterial such as polyimide, and a lamination thereof may also be used.By a droplet discharge method, different materials may be dischargedplural times to the same region to form the partition. A quarter waveplate and a half wave plate may be used as the retardation films and maybe designed to be able to control light. As the structure, a TFT elementsubstrate, the light emitting element, a sealing substrate (sealant), aretardation film (quarter wave plate), a retardation film (half waveplate), and a polarizing plate are sequentially stacked, in which lightemitted from the light emitting element is transmitted therethrough andemitted outside from the polarizing plate side. The retardation films orpolarizing plate may be provided on a side where light is emitted or maybe provided on both sides in the case of a dual emission display devicein which light is emitted from the both surfaces. In addition, ananti-reflection film may be provided outside the polarizing plate.Accordingly, a higher-definition and more precise image can bedisplayed.

As shown in FIG. 12A, a display panel 2002 using a display element isincorporated in a chassis 2001, and general TV broadcast can be receivedby a receiver 2005. When the display device is connected to acommunication network by wired or wireless connections via a modem 2004,one-way (from a sender to a receiver) or two-way (between a sender and areceiver or between receivers) information communication can beperformed. The television device can be operated by using a switch builtin the chassis 2001 or a remote control unit 2006. This remote controlunit 2006 may also be provided with a display portion 2007 fordisplaying output information.

Further, the television device may also include a sub screen 2008 formedusing a second display panel so as to display channels, volume, or thelike, in addition to the main screen 2003. In this structure, the mainscreen 2003 may be formed using an EL display panel having a wideviewing angle, and the sub screen 2008 may be formed using a liquidcrystal display panel capable of displaying images while consuming lesspower. In order to reduce the power consumption preferentially, the mainscreen 2003 may be formed using a liquid crystal display panel, and thesub screen may be formed using an EL display panel, which can beswitched on and off. In accordance with the present invention, a highlyreliable display device can be formed even when such a large-sizedsubstrate is used and a large number of TFTs or electronic componentsare used.

FIG. 12B shows a television device having a large-sized display portion,for example, a 20-inch to 80-inch display portion. The television deviceincludes a chassis 2010, a keyboard portion 2012 that is an operationportion, a display portion 2011, a speaker portion 2013, and the like.The present invention is applied to manufacturing of the display portion2011. The display portion of FIG. 12B is formed using a material whichcan be curved; thus, the television device has a curved display portion.Since the shape of a display portion can be freely designed as describedabove, a television device having a desired shape can be manufactured.

Since the display device can be formed through a simplified process inaccordance with the present invention, cost reduction can also beachieved. Therefore, the television device using the present inventioncan be formed at low cost even when formed to have a large-area displayportion. Accordingly, a television device with high performance and highreliability can be manufactured with high yield.

Naturally, the present invention is not limited to the televisiondevice, and can be applied to various use applications as large-areadisplay media such as an information display board at a train station,an airport, or the like, and an advertisement display board on thestreet, as well as a monitor of a personal computer.

This embodiment mode can be freely combined with any one of EmbodimentModes 1 to 4.

Embodiment Mode 6

This embodiment mode is explained with reference to FIGS. 13A and 13B.This embodiment mode describes an example of a module using a panelincluding the display device manufactured in Embodiment Modes 1 to 4.

A module of an information terminal shown in FIG. 13A includes a printedwiring board 946 over which a controller 901, a central processing unit(CPU) 902, a memory 911, a power source circuit 903, an audio processingcircuit 929, a transmission/reception circuit 904, and other elementssuch as a resistor, a buffer, and a capacitor are mounted. In addition,a panel 900 is connected to the printed wiring board 946 through aflexible wiring circuit (FPC) 908.

The panel 900 is provided with a pixel portion 905 having a lightemitting element in each pixel, a first scan line driver circuit 906 aand a second scan line driver circuit 906 b each of which selects apixel included in the pixel portion 905, and a signal line drivercircuit 907 which supplies a video signal to the selected pixel.

Various control signals are inputted and outputted through an interface(I/F) portion 909 provided over the printed wiring board 946. An antennaport 910 for transmitting and receiving signals to/from an antenna isprovided over the printed wiring board 946.

Note that in this embodiment mode, the printed wiring board 946 isconnected to the panel 900 through the FPC 908; however, the presentinvention is not limited to this structure. The controller 901, theaudio processing circuit 929, the memory 911, the CPU 902, or the powersource circuit 903 may be directly mounted on the panel 900 by a COG(Chip On Glass) method. Moreover, various elements such as a capacitorand a buffer provided on the printed wiring board 946 prevent a noise ina power source voltage or a signal and a slow rise of a signal.

FIG. 13B is a block diagram of the module shown in FIG. 13A. A module999 includes a VRAM 932, a DRAM 925, a flash memory 926, and the like asthe memory 911. The VRAM 932 stores image data to be displayed by apanel, the DRAM 925 stores image data or audio data, and the flashmemory stores various programs.

The power source circuit 903 generates a power source voltage applied tothe panel 900, the controller 901, the CPU 902, the audio processingcircuit 929, the memory 911, and the transmission/reception circuit 931.Moreover, depending on the specifications of the panel, a current sourceis provided in the power source circuit 903 in some cases.

The CPU 902 includes a control signal generating circuit 920, a decoder921, a register 922, an arithmetic circuit 923, a RAM 924, an interface935 for the CPU, and the like. Various signals inputted to the CPU 902through the interface 935 are inputted to the arithmetic circuit 923,the decoder 921, and the like after being held in the register 922 once.The arithmetic circuit 923 operates based on the inputted signal andspecifies an address to send various instructions. On the other hand, asignal inputted to the decoder 921 is decoded and inputted to thecontrol signal generating circuit 920. The control signal generatingcircuit 920 generates a signal containing various instructions based onthe inputted signal and sends it to the address specified by thearithmetic circuit 923, which are specifically the memory 911, thetransmission/reception circuit 931, the audio processing circuit 929,the controller 901, and the like.

The memory 911, the transmission/reception circuit 931, the audioprocessing circuit 929, and the controller 901 operate in accordancewith respective transmitted instructions. The operations are brieflyexplained below.

The signal inputted from an input unit 934 is transmitted to the CPU 902mounted on the printed wiring board 946 through the interface 909. Thecontrol signal generating circuit 920 converts the image data stored inthe VRAM 932 into a predetermined format in accordance with the signaltransmitted from the input unit 934 such as a pointing device and akeyboard, and then transmits it to the controller 901.

The controller 901 processes a signal containing image data transmittedfrom the CPU 902 in accordance with the specifications of the panel andsupplies it to the panel 900. The controller 901 generates and sends aHsync signal, a Vsync signal, a clock signal CLK, an alternating voltage(AC Cont), and a switching signal L/R to the panel 900 based on thepower source voltage inputted from the power source circuit 903 andvarious signals inputted from the CPU 902.

In the transmission/reception circuit 904, a signal transmitted andreceived as an electric wave by the antenna 933 is processed. Inspecific, high frequency circuits such as an isolator, a band pathfilter, a VCO (Voltage Controlled Oscillator), an LPF (Low Pass Filter),a coupler, and a balan are included. Among the signals transmitted andreceived by the transmission/reception circuit 904, a signal containingaudio data is transmitted to an audio processing circuit 929 inaccordance with an instruction transmitted from the CPU 902.

The signal containing audio data transmitted in accordance with theinstruction from the CPU 902 is demodulated into an audio signal in theaudio processing circuit 929 and transmitted to a speaker 928. The audiosignal transmitted from a microphone 927 is modulated in the audioprocessing circuit 929 and transmitted to the transmission/receptioncircuit 904 in accordance with the instruction from the CPU 902.

The controller 901, the CPU 902, the power source circuit 903, the audioprocessing circuit 929, and the memory 911 can be incorporated as apackage of this embodiment mode. This embodiment mode can be applied toany circuit besides high frequency circuits such as an isolator, a bandpath filter, a VCO (Voltage Controlled Oscillator), an LPF (Low PassFilter), a coupler, and a balan.

The display panel 900 includes a spacer over the pixel electrode or aninsulator covering the periphery of the pixel electrode. Accordingly, asfor a module having this display panel 900, a mask used when forming anelectroluminescent layer is supported so as not to be in contact withthe pixel electrode. Thus, the pixel electrode can be prevented frombeing damaged, and effects such as high image quality and highreliability can be obtained.

Embodiment Mode 7

This embodiment mode is explained with reference to FIG. 14. FIG. 14shows one aspect of a portable phone (mobile phone) including the modulemanufactured in Embodiment Mode 6, which operates wirelessly and can becarried. The display panel 900 is detachably incorporated in a housing1001 so as to be easily fixed to a module 999. The housing 1001 can beappropriately changed in shape and size in accordance with an electronicdevice incorporated therein.

The housing 1001 in which the display panel 900 is fixed is fit in theprinted wiring board 946 and assembled as a module. On the printedwiring board 946, a controller, a CPU, a memory, a power source circuit,and other elements such as a resistor, a buffer, and a capacitor aremounted. Moreover, an audio processing circuit including a microphone994 and a speaker 995 and a signal processing circuit 993 such as atransmission/reception circuit are provided. The display panel 900 isconnected to the printed wiring board 946 through the FPC 908.

The module 999, an input unit 998, and a battery 997 are stored in achassis 996. The pixel portion of the display panel 900 is arranged sothat it can be seen through a window formed in the chassis 996.

The display panel 900 includes a spacer over the pixel electrode or aninsulator covering the periphery of the pixel electrode. Accordingly, asfor the module having this display panel 900, a mask used when formingan electroluminescent layer is supported so as not to be in contact withthe pixel electrode. Thus, the pixel electrode can be prevented frombeing damaged, and effects such as high image quality and highreliability can be obtained.

The chassis 996 shown in FIG. 14 shows an exterior shape of a portablephone as an example. However, the electronic device of this embodimentmode can be modified into various modes in accordance with functions andapplications. In the following embodiment mode, examples of the modesare explained.

Embodiment Mode 8

Various display devices can be manufactured by applying the presentinvention. In other words, the present invention can be applied tovarious electronic devices into which the display devices areincorporated in the display portions.

Examples of such electronic devices are as follows: a camera such as avideo camera or a digital camera, a projector, a head-mounted display (agoggle type display), a car navigation system, a car stereo, a personalcomputer, a game machine, a portable information terminal (such as amobile computer, a portable phone, or an electronic book), an imagereproduction device (specifically, a device which can reproduce arecording medium such as a digital versatile disc (DVD) and includes adisplay capable of displaying the image), and the like. Examples thereofare shown in FIGS. 15A to 15D.

FIG. 15A shows a computer, which includes a main body 2101, a chassis2102, a display portion 2103, a keyboard 2104, an external connectionport 2105, a pointing mouse 2106, and the like. By using the presentinvention, a computer which has high reliability and displays ahigh-quality image even when the size thereof is reduced and the pixelis miniaturized can be completed.

FIG. 15B shows an image reproduction device having a recording medium(specifically, a DVD reproduction device), which includes a main body2201, a chassis 2202, a display portion A 2203, a display portion B2204, a recording medium (such as DVD) reading portion 2205, anoperation key 2206, a speaker portion 2207, and the like. The displayportion A 2203 mainly displays image information, and the displayportion B 2204 mainly displays character information. By using thepresent invention, an image reproduction device which has highreliability and displays a high-quality image even when the size thereofis reduced and the pixel is miniaturized can be completed.

FIG. 15C shows a portable phone, which includes a main body 2301, anaudio output portion 2302, an audio input portion 2303, a displayportion 2304, an operation switch 2305, an antenna 2306, and the like.By using the present invention, a portable phone which has highreliability and displays a high-quality image even when the size thereofis reduced and the pixel is miniaturized can be completed.

FIG. 15D shows a video camera, which includes a main body 2401, adisplay portion 2402, a chassis 2403, an external connection port 2404,a remote control receiving portion 2405, an image receiving portion2406, a battery 2407, an audio input portion 2408, an eye piece portion2409, an operation key 2410, and the like. By using the presentinvention, a video camera which has high reliability and displays ahigh-quality image even when the size thereof is reduced and the pixelis miniaturized can be completed.

This embodiment mode can be freely combined with any one of EmbodimentModes 1 to 4.

Embodiment Mode 9

Here, FIG. 16 shows a TFT using amorphous silicon for an active layer asan example of a TFT electrically connected to a light emitting element.

In FIG. 16, a reference numeral 1910 denotes a substrate; 1911, apartition; 1913, a first electrode; 1914, a layer containing an organiccompound; 1915, a second electrode; 1916, an amorphous silicon TFT;1917, a gate insulating film; and 1918, an insulating film. In addition,a reference numeral 1919 denotes a wire such as a power supply line.

In a manufacturing process for the amorphous silicon TFT 1916, a knowntechnique may be employed. First, a gate electrode is formed over thesubstrate 1910 and then the gate insulating film 1917 is formed. Next,an amorphous silicon film (active layer), a phosphorus-containingamorphous silicon film (n⁺ layer), and a metal film are sequentiallystacked. Subsequently, the amorphous silicon is etched into a desiredelement shape, and then selective etching is performed so that a part ofthe amorphous silicon is exposed in a region overlapped with the gateelectrode to form a channel. Next, the entire surface is covered withthe insulating film 1918, and then a contact hole, a source wire, and adrain wire are formed.

Note that the amorphous silicon TFT 1916 is shown as a channel-etch typeTFT, but it may be a channel-stop type TFT.

In subsequent steps after manufacturing the amorphous silicon TFT, thefirst electrode 1913 and the partition 1911 having a cross-sectionalshape which spreads toward the bottom are formed in a similar manner toEmbodiment Mode 1.

Next, the layer 1914 containing an organic compound is formed by anevaporation method, an ink-jet method, or a coating method. Then, thesecond electrode 1915 is formed by an evaporation method or a sputteringmethod.

The manufacturing process for the amorphous silicon TFT includes fewsteps at high temperature and the process is suitable for massproduction. Manufacturing cost of the light emitting device can bereduced.

In addition, since this embodiment mode explains an example of using anamorphous silicon TFT, only a pixel portion is formed over a substrateand a driver circuit is formed on an IC without forming a pixel portionand a driver circuit over the same substrate.

This embodiment mode can be freely combined with any one of EmbodimentModes 1 to 8.

This application is based on Japanese Patent Application serial no.2005-302315 filed in Japan Patent Office on Oct. 17, 2005, the contentsof which are hereby incorporated by reference.

1. A light emitting device comprising a plurality of light emittingelements over a substrate having an insulating surface, wherein thelight emitting element includes a first electrode, a partition coveringan end portion of the first electrode, a layer containing an organiccompound over the first electrode, and a second electrode over the layercontaining an organic compound, and the partition comprises a protrudingportion.
 2. A light emitting device according to claim 1, wherein thepartition has a cross-sectional shape which spreads from an uppersurface of the light emitting element toward the substrate, and has astep on a side of the partition.
 3. A light emitting device according toclaim 1, wherein an upper end portion of the partition is rounded.
 4. Alight emitting device according to claim 1, wherein the partition is asingle layer.
 5. Alight emitting device comprising a pixel portionincluding a plurality of light emitting elements over a substrate havingan insulating surface, wherein the light emitting element includes afirst electrode, a partition covering an end portion of the firstelectrode, a layer containing an organic compound over the firstelectrode, and a second electrode over the layer containing an organiccompound, and a structure made of the same material as the partition isarranged to surround the pixel portion, and a thickness of the structureand that of the partition are different from each other.
 6. A lightemitting device according to claim 5, wherein the partition has across-sectional shape which spreads from an upper surface of the lightemitting element toward the substrate, and has a step on a side of thepartition.
 7. A light emitting device according to claim 5, wherein thelight emitting device includes a substrate opposed to the substratehaving an insulating surface and the structure maintains a distancebetween the pair of substrates.
 8. A light emitting device according toclaim 5, wherein the light emitting device includes a substrate opposedto the substrate having an insulating surface and light emitted from thelight emitting element is transmitted through the substrate.
 9. A lightemitting device according to claim 5, wherein a region surrounded by thestructure and the pair of substrates is filled with a resin.
 10. A lightemitting device according to claim 5, wherein the structure is formed inthe same step as the partition.
 11. A method for manufacturing a lightemitting device, comprising the steps of: forming a first electrode overa substrate having an insulating surface; forming a partition having athick region and a thinner region using a photomask or a reticle havinga diffraction grating pattern or a semi-transmissive portion over an endportion of the first electrode; forming a layer containing an organiccompound over the first electrode; and forming a second electrode overthe layer containing an organic compound.
 12. A method for manufacturinga light emitting device according to claim 11, wherein the partition isa resin formed by selective light exposure and development using aphotomask or a reticle having a diffraction grating pattern or asemi-transmissive portion.
 13. A method for manufacturing a lightemitting device including a plurality of thin film transistors and aplurality of light emitting elements over a substrate having aninsulating surface, comprising the steps of: forming a thin filmtransistor including a semiconductor layer having a source region, adrain region, and a channel formation region therebetween, a gateinsulating film, and a gate electrode over a first substrate having aninsulating surface; forming a first electrode which is electricallyconnected to the source region or the drain region over the gateinsulating film; forming a partition which covers an end portion of thefirst electrode, and a structure in a position surrounding the pluralityof light emitting elements; forming a layer containing an organiccompound over the first electrode; forming a second electrode over thelayer containing an organic compound; and sealing the light emittingelement by attaching a second substrate to the first substrate with aresin material so that the structure maintains a distance between thesubstrates.
 14. A method for manufacturing a light emitting deviceaccording to claim 13, wherein each of the partition and the structureis a resin formed by selective light exposure and development using aphotomask or a reticle having a diffraction grating pattern or asemi-transmissive portion.